Conductive cavities



Nov. 17, 1959 J, W, DOWNI E1- AL l2,913,684

CONDUCTIVE CAVITIES 2 Sheets-Sheet 1 Filed Feb. 18, 1955 FIG.2

INVENTORS- JOHN W. DOWNIE, WINSTON I. TIRRELL,

THE TTORNEY.

FIGS

Nov. 17, 1959 J, w, DOwNlE- ETAL 2,913,684

CONDUCTIVE CAVITIES 2 Sheets-Sheet 2 LFilm1 Feb; 18, 1955 INVENTORS JOHN W. DOWNIE, WINSTON l. TIRRELL,

BY TH l TORNEY.

United States Patent Vlrice coNDUcTIvE cAvrrlEs .lohn W. Downie, EastSyracnse, and Winston I.- Tirrell, Syracuse, N.Y., assignors to General Electric Company, a corporation of New York Application February 18, 1955, Serial N o. 489,242

11 Claims.v (Cl. 333-83) .The present invention relates in general to resonant circuits of the conductive cavity type and in particular, to improved means for the tuning thereof and the coupling thereto.

`Conductive cavities are commonly used in association with electron discharge devices to furnish the resonant circuit for the functioning of the device as an amplifier,

oscillator, and the like. Commonly, electron discharge devices having disc type electrodes are utilized and the conductive cavity elements are disposed concentrically about the axis of the electrodes of the electron discharge device. With such an arrangement, the tuning of the cavity is accomplished by varying the dimensions of the cavity by some suitable variable shorting means and the coupling thereto is varied by variation in the coupling means associated with the cavity.

Conductive cavities are also commonly used in coupling the output from an amplifier to an antenna for the purpose of matching the output of the amplier to the antenna. The conductive cavity functions with the tuned output circuit of theamplier to present a higher impedance to the output of the amplifier than would otherwise be possible, thereby improving the operation of the amplier. Also, this additional tuned circuit forms with the tuned circuit of the amplifier a double tuned circuit whereby a broadening of the band of frequencies passed from the amplifier to the antenna is had as well as a sharper rejection of unwanted frequencies.

In such a matching device it is essential to be able to not only vary the frequency to which the circuit is tuned, but also to be able to vary the coupling into and out of the resonant circuit. When the resonant circuit takes the form of a conductive cavity, complications are introduced in such a device. -Conventionally, such matching devices have included a coaxial type of cavity which has sliding shorting members at each end thereof which may be varied to vary the tuning of the cavity and also have included an input and an output coupling member in association with the inner conductor of the cavity. The point at which the coupling means tap into the inner conductor may be individually varied by members extending coaxially from the ends of the shorting members of the cavity and making contact with the sliding coupling members. Y

From the foregoing illustrations, it is quite apparent that the tuning of conventional cavities entails the use of bulky members involving a number of sliding contacts and occupying a large volume, not to mention the ditiiculties experienced in the adjustment and utilization of such tuning and coupling means.

Applicants have provided improvements in conductive cavities whereby the foregoing shortcomings of conventional conductive cavities are eliminated.

An object of the present invention is to provide a simple, compact conductive cavity which has a minimum of sliding members and which is easy to tune and to couple to and from.

2,913,684 Patented Nov. 17, 1959 A further object of the present invention is to provide I simple, compact, effective resonant means which eliminates sliding trombone sections and which is easy to adjust with respect to the tuning thereof and the coupling thereto.

In carrying out the present invention as applied to an exemplary embodiment, there is provided a pair of opposed conductive members and an impedance element disposed between the conductive members. A rigid conductive cylinder is disposed between said conductive members and about said impedance element to form a conductive cavity about said impedance element. Means are provided for moving the conductive cylinder laterally between the opposed conductive members thereby to vary the position of the impedance element with respect to the conductive cylinder with resultant change in coupling and tuning. The impedance element may take the form of a capacitance, an electron discharge device, or a coupling loop.V A plurality of impedance elements may be located in the cavity and by proper adjustment of the conductive cylinder, the position of the impedance elements with respect to the conductive cylinder can be individually varied.

The features of the invention `desired tobe protected are pointed out in the appended claims. The invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof may best be understood by reference to the following description when taken iu connection with the accompanying drawings in which:

Fig. l is a sectional view of the embodiment of the present invention as applied to a conductive cavityin association with an electron discharge device;

Fig. 2 is a plan view taken along section 2--2 of Fig. l of the embodiment shown in elevation in Fig. l;

Fig. 3 is a sectional view taken along section 3-3 of Fig. 2 of a constructional feature of the embodiments of Figs. l and 2;

Fig. 4 is an elevational view in section of another embodiment of the present invention making use of a pair of conductive cavities;

Fig. 5 is a plan View of the embodiment of Fig. 4;

Fig. 6 is an elevational View in section of still another embodiment of the present invention, and

Fig. 7 is a plan view of the embodiment shown in Fi 6.

eferring now to Figs. l, 2, and 3, there is shown an illustrative embodiment of the present invention as applied to a conductive cavity in association with the output circuit ofan electron discharge device. The conductive cavity 1 comprises a pair of conductive plate members 2 yand 3 in opposed relation between which is disposed a rigid conductive cylinder 4. The plate 2 has a circular opening in the center thereof. An annular conductive member 1t) having an opening in registry with the opening of the plate 2 is disposed in insulated relationship with respect to the plate 2 by insulator 2l. A plurality of conductive ngers 5 are in conductive attachment to the inner surface of the conductive member 10. Plate 3v has an opening in the center thereof with a plurality of conductive fingers 5 disposed in conductive attachment about the opening, An electron discharge device 7 having an anode 3 and a screen grid is disposed in the openings of the plates Z and 3 to form an integral structure therewith with the disc-like plate electrode 8 making conductive contact with the conductive fingers 5 and the disc-like screen member 9 making conductive contact with the conductive lingers 6 of the plate 3. 4By provisionl of the insulator 21, separate unidirectional potentials may be applied to the electrodes 8 and 9. A conductive loop 11 is disposed within the cavity formed by members 2, 3 and 4 with one end thereof conductively attached to the cylinder 4 and the other end thereof conductively attached to the inner conductor of a coaxial transmission line 12, the outer conductor of which is attached to the conductive cylinder 4. The loop 11 functions to couple energy from the cavity. The conductive cylinder 4 has a plurality of conductive ngers 13 in sliding conductive contact with the plate 2 and also has a plurality of conductive fingers 14 in conductive sliding contact with the lower plate 3. The conductive cylinder 4 is adapted to be moved laterally between the conductive members 2 and 3 by means of a screw having one end thereof attached to the cylinder 4 and the other end thereof in threaded engagement with retaining member 16 attached to the plate 2. Turning of screw 15 is facilitated by head member 20 attached thereto or by slotting the end of the screw. The guides 22 are located on diametrically opposite sides of the cylinder 4 and each having one end rigidly fastened to plate 2 and each having a surface parallel to the axis of the screw 15 and in sliding engagement with the outside surface of cylinder 4. Thus, by turning the screw 15, the conductive plate 4 is adapted to move laterally in the guides 22 to thereby shift the position of the electron discharge device 7 in the aforementioned cavity. The nut member 17 serves to lock the conductive cylinder 4 in position once the desired position of the conductive cylinder is reached.

In the arrangement of Fig. l movement of the conductive cylinder varies the electrical position of the capacitance between electrodes and 6 in the cavity. The closer that this capacitance is disposed to the conductive cylinder, the higher will be the frequency to which the cavity is tuned and of course, when the capacitance is located at the center of the cavity, the cavity will be resonant at its lowest frequency. In this embodiment, the coupling loop 11 has been shown fixed with respect to the conductive cylinder but it may equally as well be xed with respect to the plates 2 and 3 and thereby the coupling as well as the tuning of the cavity may be varied. Also, while the cylinder 4 has been shown as capable of motion in one direction only, it will be readily understood that it may be moved in two directions as well as will become more apparent below.

The duct 18 functions to supply a cooling medium to the fins 19 in association with the anode 8 of electron discharge device 7. Insulator 21 also functions to insulate plate member 2 from the duct 18 for unidirectional potentials.

Referring now to Figs. 4 and 5, there is shown a pair of resonant circuits in accordance with the present invention with provision for varying the tuning and coupling thereof in a variety of ways. In this embodiment are shown a pair of opposed conductive plates 23 and 24 between which is disposed a conductive cylinder 25 in sliding conductive contact with the opposed members 23 and 24 and adapted to be moved laterally by means of the screw 26 having one end attached to the cylinder 25 and the other end in threaded engagement with a member 27 rigidly attached to the plate 23. The output electrodes 27 and 28 of an electron discharge device 29 are connected conductively and/or through appropriate bypass capacitances as illustrated in the anode circuit of Fig. 1, respectively, to the members 23 and 24. Thus, a resonant cavity is formed between the output electrodes of the electron discharge device. The other electrodes of the electron discharge device 29 may be associated with suitable conductive elements 30 and 31 to form an operative translating device such as an oscillator or amplilier, for example.

In this embodiment is also shown another conductive cavity comprising a pair of opposed conductive members 33 and 34 between which is disposed a conductive cyl- V2,913,684 I Y- inder 35 adapted to move in sliding engagement between the conductive members 33 and 34 by means of the screw 36. Plate 33 may be integral with plate 24. A capacitive tuning element 37 which may comprise a conductive member is attached to an insulating shaft 38, the ends of which are pivotally mounted in diametrically opposite portions of the conductive cylinder 35. Movement of the shaft 38 varies the spacing between the conductive member 37 and the plates 33 and 35 thereby varies the capacitance at the center of the cavity; thus varying the tuning of the cavity. A coupling loop 39 having one end rigidly attached to the plate 23 of the rst cavity is extended through an opening 40 in the plate 24 to make connection with one end of loop 41 in the second mentioned cavity, the other end of which is attached to the plate 34. Coupling from the second mentioned cavity is had by means of a coupling loop 42 having one end connected rigidly to the plate 34 and the other end extending through an opening 43 to make connection with the inner conductor 44 of the transmission line 45.

The arrangement described above comprises a pair of tuned circuits, the individual tuning of which and the coupling to and from which may be varied in any desired manner. While in the arrangement shown, the cylinders 25 and 35 may be moved in only one direction, it is readily apparent to those skilled in the art that the arrangement shown in Fig. 7 and to be presently described may readily be applied to the embodiments of Figs. 4 and 5 to enable the conductive cylinders 25 and 35 to be moved to any lateral position.

In the embodiment of Figs. 4 and 5, movement of the cylinder 25 varies the positioning of the capacitance of the electron discharge device 29 in the cavity and thereby varies the tuning of the cavity. Also, the coupling from the cavity is varied by means of a loop 39. The varia tion of the position of the conductive cylinder 35 varies the posiiton of the coupling of loop 41 with respect to the conductive cylinder and also varies the position of the coupling loop 42 with respect to the conductive cylinder l35. Thus, applicant has shown a simple, compact and effective means for individually tuning each of the cavities and also for individually varying the coupling to and from these cavities.

Referring now to Figs. 6 land 7, there is shown still another embodiment of the present invention as applied to a conductive cavity to and from which the coupling thereof may be independently varied. In this ligure is shown a pair of opposed plates 46 and `47 between which is disposed a conductive cylinder 48 in sliding and conductive contact with the members 46 and 47. A pair of screws 49 and `50 in threaded engagement with inembers 51 and 52, respectively, which are rigidly attached to the plate 46, are connected in engagement with the conductive cylinder 48. The members 51 and `52 disposed generally perpendicular with respect to one another have slots 61 and 62 through which screws `63 extend from the plate 46. Since the axis of the screw members 49 and 50 are differently disposed one to the other by proper adjustment of the screw members 49 and '50, the conductive ring 43 can be made to assume any lateral position between the conductive members 47 and 46. A coupling loop 53 is provided having one end connected to the member 46 and the other end connected to the inner conductor 54 of transmission line 55 through opening 56 in plate 47. Another coupling loop 57 is provided having one end rigidly attached to conductor 46 and the other end connected to the inner conductor 58 of transmission line l59 through opening 60 of plate 47. Thus, by varying the position of the ring 48, the coupling from transmission line `55 -to the cavity and from the cavity to the transmission line 59 may be readily varied. These couplings can be varied individually or simultaneously by proper adjustment of the ring 48. Cavity tuning is accomplished by means of capacitive tuning element 63a which may comprise a conductive member attached to an insulating shaft 64, the ends of which are pivotally mounted in diametrically opposite portions ofthe conductive cylinder 48.

While the impedance element above connected between the plates of the cavity and atfecting the tuning of the cavity has been shown as a capacitance, inductive impedance elements could also be used. While the coupling element shown in the embodiments above is inductive in character, capacitive coupling elements could also be used. l

It will be readily understood that while the present invention has been shown in connection with a circular type conductive cylinder that other congurations may equally be employed without departing from the present linvention. i

While we have shown and described a particular embodiment of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its broader aspects and we, therefore, aim inthe appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is: f

l. In combination, a pair of opposed conductive members, an impedance element disposed between 'said opposed conductive members, a conductive member of fixed dimensions disposed in movable relationship between said members and enclosing said impedance element, said opposed members and conductive member thereby forming a cavity about said impedance element, means for changing the position of said conductive member with respect to said impedance element.

2. In combination, a pair of conductive members, an impedance element disposed between said conductive members, a rigid cylindrical conductive member of cylindrical cross section disposed in sliding contact between said members to form a cavity about said impedance element, means for changing the position of said cylinder with respect to said impedance element.

3. In combination, a pair of opposed conductive members, a capacitance disposed between said conductive members, a rigid cylindrical conductive member disposed between said opposed conductive members and in sliding contact with each of said opposed conductive members to form a cavity about said capacitance, means for changing the position of said cylinder with respect to said capacitance thereby to change the tuning of said cavity.

4. In combination, a pair of opposed conductive members, a pair of impedance elements at least one of which is rigidly disposed between said opposed conductive members, a rigid cylindrical conductor disposed between said opposed conductive members to form a cavity about said impedance elements, means for moving said conductive cylinder with respect to said one impedance element.

5. In combination, a pair of opposed conductive members, a capacitive means disposed between said conductive members, a conductive cylinder of xed dimensions disposed between said members to form a cavity about said capacitance, coupling means in association with said conductive cavity, means for moving said cylinder with respect to said opposed conductive members.

6. In combination, a pair of opposed conductive members, a pair of impedance elements both disposed in rigid association between said conductive members, a conductive cylinder of fixed dimensions disposed between said members to form a conductive cavity about said impedance elements, means for moving said conductive cylinder lwith respect to said opposed conductive members.

7. In combination, a pair of opposed conductive members, a pair of impedance means rigidly disposed between said conductive members, a rigid conductive cylinder disposed between said members to form a cavity about said impedance elements, means for moving said cylinder laterally between said opposed conductive members.

8. In combination, a pair of opposed conductive members, a pair of impedance means rigidly disposed between said conductive members, a rigid conductive cylinder disposed between said members to form a cavity about said impedance elements, means for moving said conductive cylinder in a manner causing one of said impedance elements to move substantially more than the other of said impedance elements with respect to said conductive cylinder. Y

9. In combination, a pair of opposed conductive members, a pair of impedance means rigidly disposed between said conductive members, a rigid conductive cylinder disposed between said members to form a cavity about said impedance elements, means for moving said cylinder laterally about one of said impedance elements.

10. In combination, a pair of opposed conductive members, tuning means disposed between said opposed conductive members, a rigid conductive cylinder disposed between said members to form a conductive cavity about said tuning means, inductive coupling means in association with said cavity, means for moving said conductive cylinder laterally between said opposed conductive members to vary the position thereof with respect to said References Cited in the ile of this patent UNITED STATES PATENTS 2,410,109 Schelleng Oct. 29, 1946 2,501,181 Law Mar. 21, 1950 2,551,672 Harris et al. May 8, 1951 2,600,278 Smullin June l0, 1952 2,737,631 Beck et al. Mar. 6, 1956 2,782,383 Olive Feb. 19, 1957 

